Maintaining a hectic schedule requires effective time management and an accurate timepiece. The consequences of relying upon an inaccurate timepiece may include missing a connecting flight or arriving late to class. For example, if a passenger relies on an airport clock which is slow, then the passenger may miss a connecting flight. Likewise, if one professor relies on a clock which is slow and another professor relies on a clock which is fast, the first professor may dismiss class late while the second professor may begin class early, and students may miss the beginning of the second professor's class.
To keep everyone on time, clocks appear in a number of places. In an airport, clocks generally appear throughout the airport terminal. In a university, clocks typically appear in every classroom. In a home, a clock may be located on a wall or a bedside table or a clock may be part of an appliance, such as a microwave oven or a video cassette recorder ("VCR"). A clock must be initially set with the correct time. For example, an electric clock is typically set once power is applied. However, if the power to the clock is interrupted, then the clock must be reset. The power may be interrupted because the power fails or because the clock is disconnected to move the clock to another location. The clock must also be reset if the time changes, for example due to the start or end of daylight savings time. In a facility, such as an airport terminal or a university, every clock must be individually reset whenever power is interrupted or the time changes. In a home, every clock and every appliance including a clock must be manually reset whenever the power is interrupted or the time changes. The process of manually resetting every clock is time consuming and may result in incorrectly setting one or more of the clocks. It would be more efficient and more accurate if each clock could be automatically reset whenever the power is interrupted or the time changes.
In a facility such as an airport, the clocks located throughout the facility should be synchronized with any other devices which include a clock, such as a computer. Otherwise posted departure and arrival times may not coincide with the time displayed by the clocks. An automatic method for resetting the clocks throughout a facility would ensure that all of the clocks reflected the same correct time.
In a distributed system, data may be temporarily stored at a local site and then periodically transferred to a central site for further processing. For example, a distributed system for a chain of department stores may include point of sale terminals located throughout the department stores. For each sale, a point of sale terminal may record information about the sale, such as an inventory number, sales price, and time and date of the sale. The sales data collected during the day may be transferred to the central site at the end of the day. The sales data may be used to compile sales statistics, such as the number of sales which occurred during a particular promotion. If the time and date information recorded by the point of sale terminals is incorrect, then meaningful sales statistics cannot be compiled.
Thus, there is a need for a system and method for automatically setting and synchronizing the clocks of a variety of different devices. The time standard should be simple enough that it could be included in a home appliance without significantly increasing the size or cost of the appliance. The time standard should also be capable of transmission to a remote device.
One example of an accurate time source is the Coordinated Universal Time ("UTC") standard which is maintained by the National Institute of Standards and Technology ("NIST"). UTC is broadcast via radio stations located in Colorado and Hawaii. The broadcast signal includes seconds pulses which are transmitted every second, except on the 29th and the 59th seconds of each minute. In addition, voice announcements are broadcast once every minute. NIST also provides an automated computer time service which allows a computer to access UTC using a modem and an NIST server which allows a computer to access UTC via the Internet.
To access UTC from NIST, a device must include either a radio receiver or be capable of accessing a remote computer. Typically, an appliance, such as a microwave oven, does not have the capability of receiving a radio signal or accessing a remote computer. Even if a microwave oven could receive a radio signal, the appliance would need to convert the analog UTC signal to a digital signal to set its internal clock. Thus, there is a need for a system and method for automatically setting a clock which does not require conversion of an analog signal or access to a remote computer.